ABSTRACT: We generated MLL-AF9 mediated murine leukemias that originate either from hematopoietic stem or committed progenitors cells. The luekemia stem cell fraction in these two type of leukemias shared exactly the same immunophenotype but their genetic programs differ. Total RNA from HSC(KLS), CMP, MEP, and GMP, and from leukemia stem cells (LGMP) was isolated and hybridized to Affymetrix expresison microarrays.
Project description:Activation or maintenance of a leukemia stem cell self-renewal pathway in downstream myeloid cells is an important component of AML development We generated either MLL-AF9 mediated murine leukemias that originate from committed progenitor (GMP) cells or Hoxa9/Meis1a mediated murine leukemias that originate from hematopoietic stem cells (HSC). The leukemia stem cell fraction in these two type of leukemias shared a common self-renewal pathway with normal hematopoietic stem cells. Keywords: Cell type comparison Total RNA from HSC (KLS), CMP, and GMP, and from leukemia stem cells (LGMP) was isolated and hybridized to Affymetrix expresison microarrays.
Project description:MLL-fusion proteins can induce acute myeloid leukemias (AML) from either hematopoietic stem cells (HSC) or granulocyte macrophage progenitors (GMP), but it remains unclear if the cell of origin influences the biology of the resultant leukemia. MLL-AF9 transduced single HSC or GMP could be continuously replated, but HSC-derived clones were more likely than GMP-derived clones to initiate AML in mice. Leukemia stem cells derived from either HSC or GMP had a similar immunophenotype consistent with a maturing myeloid cell (LGMP). Gene expression analyses demonstrated that LGMP inherited gene expression programs from the cell of origin including high-level Evi-1 expression in HSC derived LGMP. The gene expression signature of LGMP derived from HSC was enriched in poor prognosis human MLL-rearranged AML in three independent data sets. Moreover, global 5’-mC levels were elevated in HSC-derived leukemias as compared to GMP-derived leukemias. This mirrored a difference seen in 5-mC between MLL-rearranged human leukemias that are either EVI1-positive or EVI1-negative. Finally, HSC derived leukemias were more resistant to chemotherapy than GMP-derived leukemias. These data demonstrate that the cell of origin influences the gene expression profile, the epigenetic state, and the drug response in AML, and that these differences can account for clinical heterogeneity within a molecularly defined group of leukemias.
Project description:Aberrant Hox gene activation is a recurrent feature in several different types of human leukemia, including leukemias with rearrangements of the mixed lineage leukemia (MLL) gene. In this study, we demonstrate that Hox gene expression is controlled by higher degree H3K79 methylation in acute myeloid leukemia (AML). We show that the deposition of progressive H3K79 methylation states at the genomic loci of critical Hox genes is dependent on the interaction of the H3K79 methyltransferase Dot1l with Af10, a protein that is found in the Dot1l complex isolated from diverse cell types. Furthermore, abrogation of the Dot1l-Af10 interaction reverses aberrant epigenetic profiles found in the leukemia epigenome and impairs the transforming ability of mechanistically distinct AML oncogenes. Primary MLL-AF9 leukemias in the AF10 floxed background (homozygous) were transduced with MSCV-IRES-tdTomato (MIT) or the Cre recombinase expressing MIT vector, cells were sorted and injected into secondary recipient mice to generate Af10 floxed (MIT) or deleted (CRE) leukemias. BM cells fresly harvested from these leukemias were sorted for tdTomato expression and used for microarrays. BM cells from Hoxa9-Meis1 transduced primary leukemias were used for comparison.
Project description:MLL-fusion proteins can induce acute myeloid leukemias (AML) from either hematopoietic stem cells (HSC) or granulocyte macrophage progenitors (GMP), but it remains unclear if the cell of origin influences the biology of the resultant leukemia. MLL-AF9 transduced single HSC or GMP could be continuously replated, but HSC-derived clones were more likely than GMP-derived clones to initiate AML in mice. Leukemia stem cells derived from either HSC or GMP had a similar immunophenotype consistent with a maturing myeloid cell (LGMP). Gene expression analyses demonstrated that LGMP inherited gene expression programs from the cell of origin including high-level Evi-1 expression in HSC derived LGMP. The gene expression signature of LGMP derived from HSC was enriched in poor prognosis human MLL-rearranged AML in three independent data sets. Moreover, global 5’-mC levels were elevated in HSC-derived leukemias as compared to GMP-derived leukemias. This mirrored a difference seen in 5-mC between MLL-rearranged human leukemias that are either EVI1-positive or EVI1-negative. Finally, HSC derived leukemias were more resistant to chemotherapy than GMP-derived leukemias. These data demonstrate that the cell of origin influences the gene expression profile, the epigenetic state, and the drug response in AML, and that these differences can account for clinical heterogeneity within a molecularly defined group of leukemias. Differential DNA methylation between of LSC isolated from murine HSC and GMP derived AMLs
Project description:The MLL gene on chromosome 11 fuses to the AF6 gene on chromosome 6 in a balanced chromosomal translocation that is characetristic of certain adult and pediatric human leukemias. We established a murine leukemia model of MLL-AF6 using the retroviral MLL-AF6 contruct in a bone marrow transplantation system. The ML2 human MLL-AF6 positive leukemia cell line was used for gene expression profiling to assess the transctiptional profile in MLL-AF6 leukemias. RNA was extracted from the ML2 cell line cultured under standard conditionswith TRIZOL (Invitrogen), purified using RNAeasy(Qiagen) and hybridized onto Affymetrix arrays.
Project description:The capacity of the hematopoietic system to promptly respond to peripheral demands relies on adequate pools of progenitors able to transiently proliferate and differentiate in a regulated manner. However, little is known about factors that may restrain progenitor maturation to maintain their reservoirs. In addition to a profound defect in hematopoietic stem cell (HSC) self-renewal, conditional knockout mice for the Pbx1 proto-oncogene have a significant reduction in lineage-restricted progenitors, including common myeloid progenitors (CMPs) and, to a lesser extent, granulocyte-monocyte progenitors (GMPs). Through analysis of purified progenitor proliferation, differentiation capacity and transcriptional profiling, we demonstrate that in the absence of Pbx1 the CMP pool is reduced due to aberrantly rapid myeloid maturation, associated with decreased expression of Meis1 and its targets including Flt3. BM cells were obtained from multiple bones of individual three to five week old Tie2Cre+.Pbx1-/f or Tie2Cre+.Pbx1+/f control mice (4-5 biological replicates/group). CMPs and GMPs were sorted by flow cytometry according to the following markers: Lin-/c-Kit+/Sca-/CD34+/CD16/32int, and Lin-/c-Kit+/Sca-/CD34+/CD16/32high, respectively, prior to RNA extraction.
Project description:The MLL gene on chromosome 11 fuses to the AF6 gene on chromosome 6 in a balanced chromosomal translocation that is characetristic of certain adult and pediatric human leukemias. We established a murine leukemia model of MLL-AF6 using the retroviral MLL-AF6 contruct in a bone marrow transplantation system. Leukemic bone marrow cells from a sacrificed moribund mouse were thawed and RNA was extracted using TRIZOL (Invitrogen) and purified further using the RNAeasy kit (Qiagen) under standard conditions and and hybridized onto Affymetrix arrays.
Project description:We generated MLL-AF9 mediated murine leukemias that originate either from hematopoietic stem or committed progenitors cells. The luekemia stem cell fraction in these two type of leukemias shared exactly the same immunophenotype but their genetic programs differ.
Project description:DNA methylation analysis on purified human long-term and short-term hematopoietic stem cells (LT-HSC, ST-HSC), common myeloid and megakaryocyte-erythrocyte progenitor cells (CMP, MEP) using HELP arrays. FACS-purified hematopoietic stem and progenitor cell (HSPC) subsets were analyzed for changes in DNA methylation using NimbleGen HELP microarrays.
Project description:RNA expression analysis on purified human long-term and short-term hematopoietic stem cells (LT-HSC, ST-HSC), common myeloid and megakaryocyte-erythrocyte progenitor cells (CMP, MEP) using microarrays. FACS-purified hematopoietic stem and progenitor cell (HSPC) subsets were analyzed for changes in RNA expression using NimbleGen gene expression microarrays.